Abstract: A housing is provided for placement over a valve in a line to prevent unauthorized access to the valve. The housing includes first and second shell halves. The first and second shell halves are mateable to form an enclosure for the valve, and to form openings through which the line can pass. Each shell half includes a perimetral lip region, an interior surface, and an exterior surface. A lock-receiving bracket is attached to the interior surface of the first shell. The lock-receiving bracket includes an aperture through which a bolt-type lock can pass. A lock-engaging member is attached to the interior surface of the second shell half. The first shell half includes an access opening for inserting the lock into the enclosure. The lock-receiving bracket is aligned with the lock-engaging bracket to permit the lock to be received by both the lock-receiving bracket and the lock-engaging member when the shell halves are mated to lock the first shell half to the second shell half.